netdev - [PATCH nf-next v3 2/7] netfilter: call nf_hook_state_init with rcu_read

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Date:   Wed, 21 Sep 2016 11:35:02 -0400
From:   Aaron Conole <aconole@...heb.org>
To:     netfilter-devel@...r.kernel.org, netdev@...r.kernel.org
Cc:     Florian Westphal <fw@...len.de>,
        Pablo Neira Ayuso <pablo@...filter.org>
Subject: [PATCH nf-next v3 2/7] netfilter: call nf_hook_state_init with rcu_read_lock held

From: Florian Westphal <fw@...len.de>

This makes things simpler because we can store the head of the list
in the nf_state structure without worrying about concurrent add/delete
of hook elements from the list.

A future commit will make use of this to implement a simpler
linked-list.

Signed-off-by: Florian Westphal <fw@...len.de>
Signed-off-by: Aaron Conole <aconole@...heb.org>
---
 include/linux/netfilter.h         | 8 +++++++-
 include/linux/netfilter_ingress.h | 1 +
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h
index 9230f9a..ad444f0 100644
--- a/include/linux/netfilter.h
+++ b/include/linux/netfilter.h
@@ -174,10 +174,16 @@ static inline int nf_hook_thresh(u_int8_t pf, unsigned int hook,
 
 	if (!list_empty(hook_list)) {
 		struct nf_hook_state state;
+		int ret;
 
+		/* We may already have this, but read-locks nest anyway */
+		rcu_read_lock();
 		nf_hook_state_init(&state, hook_list, hook, thresh,
 				   pf, indev, outdev, sk, net, okfn);
-		return nf_hook_slow(skb, &state);
+
+		ret = nf_hook_slow(skb, &state);
+		rcu_read_unlock();
+		return ret;
 	}
 	return 1;
 }
diff --git a/include/linux/netfilter_ingress.h b/include/linux/netfilter_ingress.h
index 5fcd375..6965ba0 100644
--- a/include/linux/netfilter_ingress.h
+++ b/include/linux/netfilter_ingress.h
@@ -14,6 +14,7 @@ static inline bool nf_hook_ingress_active(const struct sk_buff *skb)
 	return !list_empty(&skb->dev->nf_hooks_ingress);
 }
 
+/* caller must hold rcu_read_lock */
 static inline int nf_hook_ingress(struct sk_buff *skb)
 {
 	struct nf_hook_state state;
-- 
2.7.4